1. Field of the Invention
The present invention relates generally to the reduction of corrosion of metal alloys used during acidizing treatments of wells.
2. Description of the Related Art
Aqueous acidic solutions are frequently applied to treat wells and to remove formation damage during well completions or subsequent workovers. Acid treatment of a well involves the pumping downhole of an aqueous acidic solution that reacts with the subterranean formations, such formations usually consisting of limestone or sand, to increase the size of the pores within the formations and provide enlarged passageways for hydrocarbon, water, or steam to more freely move to collection points that would otherwise be obstructed. Depending on the types of treatments and the nature of formation damage, the aqueous acidic solutions can be hydrochloric acid (HCl), hydrochloric-hydrofluoric mud acid (HCl—HF), organic acids such as acetic acid and formic acid, or combinations thereof. A problem associated with acid treatments is the corrosion by the acidic solution of the metal tubular goods in the wellbore and the other equipment used to carry out the treatment. The corrosion problem is exacerbated by the elevated temperatures and pressures encountered in deeper formations. In the wellbore, the tubular materials used are normally carbon steel or alloy steel. The cost of repairing or replacing corrosion-damaged casing, tubing, and other equipment in the wellbore is extremely high.
Various acid compositions that include corrosion inhibitors for diminishing the corrosive effects of the acid on metal surfaces have been developed and used previously. The types of components employed in corrosion inhibitors vary depending upon the nature of the compositions, the types of metal surfaces involved, associated environmental conditions, and so forth. In some prior attempts to reduce corrosion by using corrosion inhibitors, various problems exist, such as having high toxicity ratings or not being environmentally friendly. Some prior art corrosion inhibitors are also cationic, which makes them incompatible with various other acid treatment additives, such as with anionic anti-sludge agents.
A need exists for new and useful compositions for inhibiting or preventing corrosion during the acid treatments of wells with safer, less toxic, and more environmentally acceptable acid treatment fluid compositions. It is also desirable for the compositions to be compatible with other additives that are used in acid treatments.